The present invention is generally directed to fire detection systems and more particularly to, an improved alarm system for use in such fire detection systems. The present invention is capable of providing a plurality of alarm indications each associated with a different condition of a remote sensor. The present invention is further capable of providing an advanced warning of an impending fire.
There are many applications in today's industry and commerce for fire detection systems. Such systems are customarily employed, add in fact are generally required by local fire protection laws, in commercial establishments such as factories or office buildings where a large number of people are employed. Such systems are also commonly used in warehouses where valuable inventory is to be protected against loss due to fire.
Fire detection systems used in the commercial environment generally include a plurality of remote sensors which are arranged to sense the level of a parameter of a fire condition such as, for example, heat or smoke density. The remote sensors are distributed throughout the protected area and each sensor is coupled to a central control unit by a communication link. One or more of the remote sensors may be coupled to any given one communication link.
Each sensor is assigned a unique address to permit interrogation by the central control unit and transmits, when interrogated, electrical signals indicative of the level of the parameter being sensed. One common parameter sensed by such sensors is smoke density. The transmitted electrical signal can be, for example, a pulse width modulated signal wherein the length of the transmitted pulse is indicative of the level of the sensed parameter.
The central control unit generally includes software which compares the sensed level received from the sensor to a predetermined fire alarm level or limit. When the level sensed by a remote sensor exceeds the limit, the central control unit will determined the location of the remote sensor by its address, initiate an appropriate fire alarm to evacuate the entire premises or only the affected area, and notify the proper fire department authority.
While fire detection systems of the type referred to above have been generally successful, there remains room for improving their operation and available features. Firstly, such systems are only able to provide an alarm indication when there is an actual fire in process, limiting the amount of time for personnel to evacuate the affected premises. Secondly, current systems are incapable of providing an indication of a situation which is suspected of being a potential fire. Such an indication would allow appropriate maintenance personnel to inspect the relevant area for a condition which may lead to a fire. Such an indication could possibly avoid a fire altogether and, therefore, would not require evacuation by the personnel at that location. Lastly, remote sensors, especially those adapted to sense smoke density, have a tendency to drift in their calibration or to become covered with dust or other particulative matter suspended in the air surrounding the sensors. These conditions can lead to possible false fire indications. It would be most desirable for the fire detection system in which such sensors are employed to have the capability to notify maintenance personnel if one of these conditions exists so that maintenance personnel could provide the appropriate required maintenance to the sensor.
It is therefore a general object of the present invention to provide a new and improved alarm system and method for use in a fire detection system.
It is a further general object of the present invention to provide such a system and method which allows an advanced warning of an impending fire to thereby provide an early fire warning.
It is a further object of the present invention to provide such a system and method which allows a pre-fire condition to be sensed and indicated to afford maintenance personnel an opportunity to rectify a potential fire condition before an actual fire ensues.
It is a further object of the present invention to provide an alarm system and method for use in a fire detection system which allows a required sensor maintenance condition to be detected and indicated to notify maintenance personnel when maintenance of a remote sensor is required.